I Agree...
50 years is not that long for a lot of things here... even if newer versions come along they take a while to become the "norm"...
In terms of Destroyers the closest equivilent i can think of would be the B-52 - These have been in service ~60 years already and have just been extended until ~2040 (please correct me if i'm wrong here!) although the avionics are completely new the airframe is the same...
In other transport - the InterCity 125 - originally built in 1975 (40 years ago!) they are still in use down here in cornwall and will be for at least another 10 - 20 years as they are due another refit soon!...
I can easily imagine things stagnating after (still during?) the collapse of the empire while a new power takes over - what ever that may be...